Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual é a quantidade da classe B V?
 ###Tabelas: CREATE TABLE u.s._presidents (u.s._presidents_id AUTO_INCREMENT PRIMARY KEY, Name VARCHAR, Deceased Spouse VARCHAR, Cause of Death VARCHAR, Date of Spouses Death VARCHAR, Length of Marriage VARCHAR, Children Together VARCHAR, Current Marital Status VARCHAR) CREATE TABLE 1937_ladder (1937_ladder_id AUTO_INCREMENT PRIMARY KEY, Club VARCHAR, Wins INT, Losses INT, Draws INT, Against INT) CREATE TABLE locomotives_of_the_early_period_for_all_types_of_train (locomotives_of_the_early_period_for_all_types_of_train_id AUTO_INCREMENT PRIMARY KEY, Class VARCHAR, Number(s) VARCHAR, Quantity VARCHAR, Year(s) of Manufacture VARCHAR, Type VARCHAR) CREATE TABLE "_"_45_nm ("_"_45_nm_id AUTO_INCREMENT PRIMARY KEY, Model number VARCHAR, sSpec number VARCHAR, Frequency VARCHAR, Turbo VARCHAR, Cores INT, L2 cache VARCHAR, L3 cache VARCHAR, I/O bus VARCHAR, Mult. VARCHAR, Memory VARCHAR, Voltage VARCHAR, Socket VARCHAR, Release date VARCHAR, Part number(s) VARCHAR, Release price ( USD ) VARCHAR) CREATE TABLE member_schools (member_schools_id AUTO_INCREMENT PRIMARY KEY, Institution VARCHAR, City VARCHAR, State VARCHAR, Team Name VARCHAR, Affiliation VARCHAR, Enrollment INT, Home Conference VARCHAR)  
SELECT Quantity FROM locomotives_of_the_early_period_for_all_types_of_train WHERE Class = b v